1. Field of the Invention
The present invention relates to radiation imaging apparatuses and radiation imaging systems using X-rays, α-rays, β-rays, γ-rays, and the like.
2. Description of the Related Art
In various medical fields, digitization of information has recently been advanced. For example, in the field of X-ray diagnosis using radiation, a two-dimensional radiation imaging apparatus has been developed for digitizing image information. A radiation imaging apparatus of a forty-three-cm square at most has been developed for use in mammography and chest radiography.
Such an imaging apparatus comprises a plurality of imaging elements which are arranged in a tile-like form to provide large-area radiation imaging. The imaging elements include CCD imaging elements, MOS imaging elements, CMOS imaging elements, and the like.
Radiation imaging for medical diagnosis is frequently performed by, for example, a film screen system comprising a combination of an intensifying screen and a radiographic film. In this system, X-rays transmitted through an object contain information regarding the inside of that object, and the X-rays are converted into visible light proportional to the strength of the X-rays by the intensifying screen to expose the X-ray film to the visible light.
Also, an X-ray digital imaging apparatus has recently come into use, in which X-rays are converted into visible light proportional to the strength of the X-rays by a fluorescent material, converted into electrical signals by a photoelectric transducer (photodiode), and then converted into digital signals by an analog-to-digital (A/D) converter.
U.S. Pat. No. 4,810,881 discloses such an imaging apparatus comprising a plurality of imaging elements.
FIG. 13 shows the example disclosed in U.S. Pat. No. 4,810,881 in which a plurality of modules each comprising a glass substrate and a member of a fluorescent material or the like formed on the glass substrate are connected. FIG. 13 is a sectional view taken along the arrangement direction of the modules.
In FIG. 13, reference numeral 3 denotes a reading means; reference numeral 4, a module; reference numeral 5, a glass substrate; reference numeral 6, an X-ray shield; reference numeral 8, a connection line for connecting a line connection portion 30 and the reading means 3; reference numeral 30, the line connection portion; reference numeral 80, a transparent conductive layer; reference numeral 90, a photo-detection layer; and reference numeral 107, a scintillator. A combination of a plurality of these modules provides a large-area X-ray imaging apparatus.
In the conventional technique shown in FIG. 13, the scintillator is uniformly formed on each of the modules. However, when the scintillators are formed after the glass substrates (imaging elements) are combined, the scintillators cannot be uniformly formed in the spaces between the adjacent imaging elements because spaces for passing the connecting lines are present between the respective glass substrates. Therefore, nonuniformity occurs in the scintillators near the spaces, and a uniform light quantity distribution cannot be obtained. In this specification, “nonuniformity in the scintillators” represents discontinuity of crystallinity or thickness of the scintillators.
When a planarizing layer is formed on a plurality of spaced apart imaging elements in order to uniformly form the scintillators, the planarizing layer cannot be easily formed because an adhesive or an organic resin rises in an external terminal disposed on each of the spaced apart imaging elements. Particularly, it is difficult to form the planarizing layer by bonding an adhesive sheet as an adhesive.